Previous work has established that right middle cerebral artery ligation in the rat leads to depletions of catecholamines and behavioral alterations in spontaneous activity and shock-elicited aggression. Pharmacological studies have indicated that catecholaminergic neurons play an important role in these behavioral changes. In recent studies, we have demonstrated that spontaneous hyperactivity can be elicited by lesions of the right hemisphere but not the left hemisphere. This behavioral asymmetry strongly suggests that there is an underlying biochemical or structural asymmetry of the brain perhaps within the catecholaminergic pathways. This proposed research project will study the relationship between these changes in catecholamines and alterations in behavior following experimental cerebral infarction of either the right or left hemisphere. Two areas of investigation are proposed. The first series of experiments will compare the effects of right vs left middle cerebral artery ligation on catecholamines and behavior utilizing a variety of behavioral tests, and a radio-enzyme assay for catecholamines. The second series of experiments will determine whether specific lesions of catecholamine terminals in the cerebral cortex by 6-hydroxydopamine has the same behavioral and biochemical effects as cerebral infarction.